Heart valve replacement surgery involves the replacement of the native valves of the heart with a prosthetic valve. Prosthetic valves include mechanical valves involving only metals and polymers, and tissue valves that include non-synthetic, biocompatible materials such as pericardium, or bovine, equine or porcine tissue. Some patients have a relatively small aortic root due to their particular anatomy or excessive calcification. Some patients (e.g., young children) are likely to outgrow a prosthetic valve or outlive the useful life of a prosthetic valve.
U.S. Pat. No. 5,383,926 (Lock et al.) discloses a re-expandable endoprosthesis. The endoprosthesis is said to be re-expandable to accommodate vessel change.
U.S. Patent Application Publication Nos. 2003/0199971 A1 (Tower et al.) and 2003/0199963 A1 (Tower et al.) describe a valved segment of bovine jugular vein mounted within an expandable stent, for use as a replacement heart valve. Replacement pulmonary valves may be implanted to replace native pulmonary valves or prosthetic pulmonary valves located in valved conduits as described, for example, in “Percutaneous Insertion of the Pulmonary Valve”, Bonhoeffer, et al., Journal of the American College of Cardiology 2002; 39: 1664-1669.
Degenerated and stenotic valves in conduits or in valved stents potentially allow for a second valved stent implantation without the need for surgery, as described, for example, in “Transcatheter Replacement of a Bovine Valve in Pulmonary Position”, Bonhoeffer, et al., Circulation 2000; 102: 813-816. It has been proposed that sequential percutaneous pulmonary valve implantation is feasible and theoretically could delay the need for invasive surgery indefinitely, thus overcoming concerns regarding conduit longevity and risks associated with reoperation, as described, for example, in “The potential impact of percutaneous pulmonary valve stent implantation on right ventricular outflow tract re-intervention”, Coates, et al., European Journal of Cardio-thoracic Surgery 27 (2005) 536-543.
U.S. Patent Application Publication No. 2003/0199971 A1 (Tower et al.) discloses a stented valve with an ability to be reconfigured after implantation. This is identified as a feature useful in cases where a valve has been implanted in a growing patient (e.g., a child). Rather than replacing a valve periodically during the growth period, the supporting stent may be reconfigured to accommodate growth using a percutaneously introduced balloon catheter for re-engaging the stent to reconfigure the stent so that it will conform to the changes in the implantation site produced by the growth of the patient. In an article by Bonhoeffer, et al. entitled “Percutaneous Insertion of the Pulmonary Valve” J Am Coll Cardiol, 2002; 39:1664-1669, the percutaneous delivery of a biological valve is described. The valve is sutured to an expandable stent within a previously implanted valved or non-valved conduit, or a previously implanted valve. Again, radial expansion of the secondary valve stent is used for placing an maintaining the replacement valve.
Stented valve systems involving two or more components are disclosed in U.S. Patent Application Nos. 2004/0030381 A1 (Shu et al.) and 2008/0004696 A1 (Vesely et al.); U.S. Pat. No. 6,530,052 (Khou et al.) and U.S. Pat. No. 7,011,681 (Vesely et al.) and PCT Publication Nos. WO 06/0127756 A2 (Rowe et al.), WO 07/0181820 (Nugent et al.) and WO 07/130537 (Lock et al.). Some of these valve systems describe the reuse of a portion of their system. Some of these valve systems require the removal of an element and its replacement by a different element. It is believed that transcatheter removal of a previously implanted stented valve component creates challenges such as damage to implant site, creation of sites for thrombus/emboli formation and release, paravalvular leakage, inability to access removable elements due to tissue ingrowth and/or complex navigation, and delivery difficulties.